Spring Boot Handbook

What is Spring Boot? 

Spring Boot is a Java-based framework that helps developers build production-ready applications quickly without worrying about complex configurations.

Think of it as Spring Framework on steroids — with auto-configuration, embedded servers, and ready-to-use tools.

• Spring = A powerful but complex toolbox.

• Spring Boot = A smart assistant that picks the right tools and sets them up for you.

Why is Spring Boot Important?

• Traditional Spring Framework requires a lot of XML configurations and setup.

• Spring Boot removes this pain by:

  • Auto-Configuration → It configures your app automatically based on dependencies.

  • Rapid Development → Just run your app like a normal Java program (main method).

  • Embedded Server → No need to deploy WAR files to external servers like Tomcat.

  •  Production-ready Features → Health checks, metrics, monitoring out-of-the-box.

Imagine building a house. With Spring, you buy all materials, tools, and hire workers yourself.
With Spring Boot, you get a ready-made house with electricity, plumbing, and furniture — you just move in and decorate.

Real-World Example

Suppose you want to build a REST API for a Train Reservation System:

• In traditional Spring:

  • Configure Tomcat, DataSource, Hibernate, JSON parser, DispatcherServlet, etc.

  • Takes hours/days.

• In Spring Boot:

  • Add dependency → spring-boot-starter-web

  • Write your controller → Run → Done 

// Simple Spring Boot REST API
@SpringBootApplication
public class TrainReservationApp {
    public static void main(String[] args) {
        SpringApplication.run(TrainReservationApp.class, args);
    }
}

@RestController
public class TrainController {
    @GetMapping("/trains")
    public String getTrains() {
        return "List of available trains";
    }
}

Run the app → it starts with an embedded Tomcat server → API available at http://localhost:8080/trains.

Key Features of Spring Boot

1. Starters – Predefined dependencies for common use cases (spring-boot-starter-web, spring-boot-starter-jdbc).

2. Auto-Configuration – Reduces manual setup (picks defaults based on classpath).

3. Embedded Servers – Tomcat, Jetty, Undertow included.

4. Actuator – Health check, metrics, monitoring endpoints.

5. Spring Boot CLI – Run Groovy scripts directly.

6. Spring Initializr – Online project generator (start.spring.io).

Conclusion

• Spring Boot = Rapid Application Development with Spring.

• Removes boilerplate setup with starters and auto-configuration.

• Includes embedded servers → no WAR files.

• Provides production-ready features (Actuator, metrics, health checks).

• Perfect for REST APIs, Microservices, and Cloud-Native Apps.

 If Spring was the engine, Spring Boot is the car with automatic gears, AC, and GPS — you just drive